Photographic elements bearing a polyvinylpyridine sublayer, a layer containing a soluble boron compound and a silver halide synthetic hydroxyl polymer layer and their preparation



Sept. 7, 1948. c. F. GLICK 2,448,525 PHOTOGRAPHIC ELEMENTS BEARING Arouvmvmmmmm SUBLAYER, A LAYER CONTAINING A sowsm sonon comrouun AND Asnmm HALIDE snmmnc nmnoxu rommma LAYER AND THEIR PREPARATION Filed Nov;27, 1946 POLYVINYLACETAL COLOR FORMER AND SELVER HALIDE HYDROLYZEDETHYLEN INYL ACETATE AND DIETHYLENE GLYCOL 8 RAX-BOR|C ACIDPRODUCTPOLYVINYLPYRIDINE LAYER GELLULOSE NITRATE FILM BASE v INVENTOR. CHARLESF. GL/CK A T TORNE Y ?atented Sept. 7, 1948 PHOTOGRAPHIC ELEMENTSBEARING A POLYVINYLPYRIDINE SUBLAYER, A LAY- ER CONTAINING A SOLUBLEBORON COM- POUND AND A SILVER HALIDE SYN- THETIC HYDROXYL POLYMER LAYERAND THEIR PREPARATION Charles F. Glick, New Brunswick, N. J., assignorto E. du Pont de Nemours & Company, Wilmington, DeL, a corporation ofDelaware Application November 2:, 194a, Serial No. mass 9 Claims.

This invention pertains to photographic elemcnts and to theirpreparation. More particularly. it pertains to photographic elementsbearing synthetic hydroxyl polymer layers and to their preparation.

The coating of synthetic hydroxyl polymer layers, and especially silverhalide emulsion layers, is difficult to carry out on a commercial scale.It is also quite difficult to obtain a satisfactory degree of permanentadherence of such layers to the support. Synthetic hydroxyl polymers, e.g., polyvinyl alcohol and derivatives and interpolymers thereof, do notgel or set like gelatin with slight lowering of temperature. Whenelevated temperatures are used to drive off the solvent, hydroxylpolymers can be coated fairly rapidly but the layers tend to be tricky.It has been proposed to add various types oi gelling agents to practice,while useful for small operations, has

some disadvantages for large-scale commercial operations. The emulsionssometimes gel or set up in the containers or coating apparatus. Thelayers lack uniformity because the gelling agents continue to act.

An object of this invention is to improve the art of coating synthetichydroxyl polymers. A more specific object is to improve the art ofcoating synthetic hydroxyl polymer silver halide emulsions. A furtherobject is to improve the anchorage of such polymer layers to supports. Arelated object is to provide photographic supports with gelled layerscomposed of synthetic hydroxyl polymers which are permanently anchoredtheretd. Another object is to provide processes for preparing suchelements which can be carried out as a continuous commercial operation.Still other objects will be apparent from the more detailed descriptionof the invention.

The above objects are attained by the preparation of photographicelements comprising a support havin deposited thereon a sublayercomposed of a vinyl-pyridine polymer on which is coated an intermediatelayer composed of a synthetic hydroxyl polymer colloid which carries agelled light-sensitive. synthetic, hydroxyl polymer colloid silverhalide emulsion layer.

The novel elements are advantageously prepared by dissolving avinylpyridine polymer in a solvent, e. g., water-miscible alcohol oracetone or mixtures thereof, in an amount of 0.25 to 20% by weight ofthe alcohol. A 2 to 5% solution in acetone-ethanol containing 40 to 60parts of the former per 60 to 40 parts of the latter by weight beingquite practical. The resulting solution is then deposited on a support.for example, a illm base or sheet or paper and dried. An aqueoussolution of a water-soluble or hydrophilic synthetic hydroxyl polymer isprepared and material amounts of a soluble boron compound which formborate ions in aqueous solution admixed therewith are deposited on thevinylpyridine polymer layer. An aqueous solution of a synthetic hydroxylpolymer colloid which has light-sensitive silver halides dispersedtherethrough is de posited on the intermediate layer. The pH 0! thelayers is adjusted so that the light-sensitive layer is alkaline. Thus,if the pH of the intermediate layer is on the alkaline side. a neutralalkaline or slightly acidic colloid silver halide emulsion is depositedthereon. The layer can be made alkaline after coating by impregnating itwith an aqueous alkaline solution. e. 3.. a sodium carbonate solution.The soluble boron compound diii'uses and causes gelling oi the emulsionlayer.

In case an acidic emulsion layer is coated, the boron compound should besufllciently alkaline to result in a final pH of at least 7.0 andpreferably of at least 7.5.

. In the preferred form of the invention a support is first coated witha vinylpyridlne polymer sublayer. An aqueous solution of a synthetichydroxyl polymer containing a soluble boron compound and having a pH ofnot more than 6 is coated on the sublayer to form a gelling intermediatelaye'r. An aqueous solution of an alkaline hydroxyl polymer silverhalide emulsion having a pH of more than 7.5 is coated onto theintermediate layer. The layer gels rapidly as the coating is applied andtakes effect from the bottom up. In general. adequate gelation occurs inless than 60 to seconds.

The vinylpyridine polymers can be made by polymerizing a monomericvinylpyridine, e. g., alpha-, beta or gamma-vinylpyridlne or a homologuethereof containing an alkyl radical of one to four carbon atoms in thepyridine ring,

in a liquid medium by the aid of a polymerization.

catalyst. An or anic solvent solution can be used if desired in whichcase inert organic solvents are used. However, emulsion polymerizationis quite useful and bulk polymerization methods are effective. Thepolymerization is preferably carried out in an aqueous mineral acidsolution or medium in the presence of a peroxy compound 7 catalyst attemperatures from about 20 to 50 C. for a period of ten or less to 200or more hours. The proportion of mineral acid, e. g. hydro- 3 chloric orsuli'uric, may vary over a iairly wide range, e. g., from 0.6 to 2.5mols acid per mol oi vinylpyridine monomer. The resulting solution maybe diluted with water and the solution added to a basic solution. e. g.,aqueous sodium hydroxide. and the precipitated resin filtered,

washed, and dried. A neutralizing agent can be present in the washwater.

The invention is not limited to the use of polyvinylpyridine, includingthe alkyl substituted polyvinylpyridines, as the binding agents for theantihalation materials because copolymers soluble in 1% aqueous aceticacid which contain up to 20% of another polymerizable vinyl orvinylidene compound having a single vinyl group (CH:==C are useful.Suitable compounds for copolymerisation with a monomeric vinylpyridineare styrene, acrylic esters and amides, alpha-allryl-substituted acrylicesters and amides, acryionitrilee, and 'methacrylonitriles.

In making the copolymers there may be used such materials as methyl orethyl acrylates; methyl, ethyl isobuty-l, and methoxyethylmethacrylates; methacrylamide and N-methylacrylamide: acrylonitrile andmethacrylonitrile; styrene, vinyl naphthalene, and the like or mixturesof two or more of these compounds.

In a preferred aspect oi the invention the polymers oi unsubstitutedalpha or 2-vinylpyridine or its interpolymers containing 1 to 0! adiflerent interpolymerizable monomer are used.

Such polymers are non-water-soluble synthetic resins soluble inalcohols, e. g., methyl, ethyl, propyl, and butyl, and mixtures of suchalcohols with ketones, e. g., acetone, methyl ethyl ketone, methylpropyl ketone, and methyl isobutyl ketone or in certain chlorinatedhydrocarbons, e. g., trichlorethylene. They form clear, lightcolored,non-tacky films or coatings which are readily and completely soluble indilute aqueous acids, e. g., acetic, hydrochloric, suliamlc, sulfuric,phosphoric, and oxalic acids.

Synthetic hydroxyl polymers oi the type comprehended by the inventionare harddilm form- 8 P lymers which contain a plurality oi recurringaliphatic hydroxyl groups as the predominant hyclrophilic group. Thepreierred synthetic hydroxyl polymers contain a plurality of recurringvinyl alcohol units (-cm-c'mon) Polyvinyl alcohol and its lower fattyacid esters and lower alkyl ethers and acetels are especially usefulpolymers of this tym. Polyvinyl alcohol is a tough-,water-white,resin-like material. It is soluble in water. The more highly polymerizedvarieties are soluble in hot water and the medium or lower polymers aresoluble in cold water. They are usually prepared by hydrolysis ofpolyvinyl esters, such as polyvinyl acetate, polyvinyl chloracetate,polyvinyl isobutyrate, etc. The partly hydrolyzed esters which contain alarge number of recurring vinyl alcohol units are water-soluble incharacter. The ethers can be made by incompletely etheriiying thecompletely or partially hydrolyzed polyvinyl acetate. etc. The polyvinylacetals, e. g., polyvinyl acetaldehyde acetal and polyvinyl isobutyral,can be made by acetalization of polyvinyl and its incompletelyhydrolyzed carboxylic acid esters.

In addition to the water-soluble synthetic hydroxyl polymers Justdescribed, there may be mentioned partially and completely hydrolyzedpolyvinyl ester, -e. g.. polyvinyl acetate interpolymers withethylenically unsaturated compounds, such as vinyl chloride and styrene;acrylic acid esters. e. g., methyl acrylate; methacl'ylic acid esters,e. g., methyl methacrylate; and mono-olennes, e. g., ethylene. Thecompletely hydrolyzed ethylene/vinyl acetate interpolymer emulsiondescribed in McQueen 2,397,866 and Roland 2,386,347 form an importantclass 01' silver halide emulsions which can advantageously be coated bythe improved methods in question. These polymers may containcolor-former nuclei. Suitable polymers of this type are described inUnited States Patents 2,310,943, 2,397,864, 3,397,685 and 2,320,422 andin United States appiication Serial Number 528,946 new Patent No.2,415,381.

The synthetic hydroxyl polymers set forth above are characterized by thepresence oi a large number oi iree aliphatic hydroxyl groups which arepresent in recurring vinyl alcohol Lem-$K) units.

While boric acid and borax containing sublayers having a pH less than 6are useiul for gelling the coated vinyl alcohol polymer silver halideemulsion layers, it has been found that the boric acid esters ofpolyhydric alcohols are eminently well suited for this purpose and causea rapid gelling oi the silver halide emulsion layers. Such esters can beprepared by reacting a polyhydric alcohol, e. g., ethylene glycol,diethylene glycol, triethylene glycol, erythrol, sorbitol, and mannitolwith boric acid or a mixture of boric acid and borax, by heating theadmixture to 100 to C. A copious evolution of water occurs. Theresulting products are viscous syrups cl resins of a colloidal natureand have a high molecular weight and complex structure. They are readilysoluble in water but are substantially insoluble in hydrocarbons butprobably hydrolyze to the boric acid and glycol in water. Theirpreparation is described in various United Etetee Patents including1,953,741, 2,223,349, 2,233,948, 2,223,949, and 2,224,011. Thesecompounds have been referred to as borlborates.

in order to reduce the pH of the sublayer to the desired level, theremay be added to the sublayer a small amount of a readily soluble acid,e. g., glyoolic acid, acetic acid, diglycolic acid, etc., or acidreacting salts, e. g., ammonium nitrate and ammonium chloride.

The soluble boron compounds are used in amounts sumcient to givecomplete gelling of the over-coated synthetic hydroxyl polymer-silverhalide emulsion layer. The amounts, of course, vary in accordance withthe particular hydroxyl polythey emulsion to be gelled. In general,amounts from 20 to 60% by weight of the polymer in the sublayer aresufilclent to gel the silver halide emulsion coatings.

The invention will be iurther illustrated but is not intended to belimited by the following exampics. The parts are by weight.

Example I All cellulose nitrate illm base I as shown in Fig. 1 oi theaccompanying thawing is coated with a solution consisting oi three partsof polyvinylpyridine, so parts of acetone, and 57 parts of ethanol toform a thin sublayer 2. Fifty cubic centimeters (50 cc.) of a solutionoi ten parts of a hydrolyzed ethylene/ vinyl acetate lnterpolymerassasss oi the type described in Example I oi McQueen United StatesPatent 2,897,880 in ten parts ethanol and 80 parts 01' water are mixedwith 1.65 grams oi. glycolic acid and 115 cc. oi aqueous solutioncontaining 2.5 parts of diethylene glycolboraz-boric acid condensationproduct prepared as described in United States Patent 1.958,! by heatingthe admixture to 100" to 160' C. The resulting solution is coated ontothe sublayer to term an intermediate gelling layer 8. A ilowablephotographic silver halide emulsion in the same interpolymer is. made asdescribed in Example I oi the aforesaid McQueen patent in an amount oililo cc. and mixed with 15 cc. oi water and 3 cc. of BNKOH and coatedonto the dried intermediate layer to form emulsion coating 4. Theemulsion begins to gel as the coating is applied and proceeds from thebottom upward. A iirm gelled emulsion is formed in about two minutes.The sublayers are clear and non-tacky. Good wet and dry anchorage existsbetwen the dim base and the coated layers.

The diethylene glycol boriborate is made by reacting diethylene glycolwith'a mixture oi boric acid and borax by heating the admixture to 100to 1%" C., whereby a copious evolution oi water occurs. as described inUnited States Patent isomer.

Example I! A cellulose nitrate iilm base is provided withapolyvinvlpyridine sublayer as described in Example I. To lid cc. 0!2.5% aqueous solution of diethylene glycol-borax-boric acid condensationproduct, described in Example I, are added 1.22

.elwn the interpolymor 0! Example I in ten parts of ethanol and 80 partsoi. water and 0.5 cc. of a 16% aqueous solution of N-cetylbetaine. Theresulting solution is coated onto the aforesaid sublayer and dried toform an intermediate layer. A solution of a photographic emulsion isprepared and coated as described in Example I with similar results.

Emmple III A cellulose nitrate film base is provided with apolyvinylpyridine sublayer as described in Example I. An intermediategelling layer is coated on the sublayer irom a coating solution made bymixing 75 cc. of ethanol. 2.9 cc. of diethylene giycol-borax-boric acidcondensation product of Example I, 37 cc. of water, 0.83 gram ofglycolic acid, and adding the mixture to 50 cc. of ten parts of theinterpolymer of Example I, ten parts of ethanol, 80 parts oi water, and0.5 cc. of a aqueous solution of N-cetylbetaine.

A silver halide emulsion in a hydrolyzed ethylene/vinyl acetateinterpolymer is prepared as described in Example I and 150 cc. oi it ismixed with cc. oi a 6.7 aqueous solution oi triethanolamine and 0.75 cc.of a 10% aqueous solution of N-cetylbetaine. The nowable emulsion iscoated onto the intermediate layer. The coating gels rapidly as theemulsion is applied. A nrm gelled layer forms in about 30 seconds. Thesublayer and intermediate layer are clear and nontacm. Good wet and dryanchorage between all layers is noted in the raw and photographicallyprocessed stock.

Example IV A cellulose nitrate film base I as shown in Fig. 2 oi theaccompanying drawing is provided with a polyvinylpyridine sublayer I andan intermediate gelling layer I as described in Example 111. Silverhalides are dispersed in a hydrophilic polyoi diglycolic acid, 50 cc. oiten parts oi pared as described in Martin Serial Number 682,137, illedJuly 8. 1940, alter the manner described in Jennings et al. UnitedStates Patent 2,307,864. one hundred cubic centimeters (100 cc.) oi thisemulsion was mixed with 6.7 cc. of triethanclamine solution containingone part oi the former in nine parts oi water. The' resulting colori'orming light-sensitive silver halide dispersion is coated onto thegelling intermediate layer. The polyvinylacctal color former layer 4'gels from the bottom upward as it is applied and a firm gel layer formsin about 30 seconds. The

resulting element has good wet and dry anchorage of all layers.

Similar results are obtainable by substituting other hydrophilic colorformer polymers including the hydrophilic mixed acetal oim-(benzoylacetamidolbenzaldehyde and o-suliobenzaldehyde (Na salt) withpolyvinyl alcohol described in McQueen Serial Number 667,126, i'lled May3, 1946.

In place of the specific gelling agents described above, there may besubstituted other boric acid esters or salts capable 0i yielding borateions in aqueous solution. Suitable additional compounds includesodiumand potassium tetraborate, metaborate. and orthoborate, boricacid, glyceryl borate, glycerol boriborate; the sorbitol, mannitol, anddulcitol monoborate and diborates and monoand poly-condensation productsand their sodium and ammonium salts set forth in Examples 1 to 19 oiUnited States Patent 2,223,349 and Examples 3, 4, i5, 7, 9, l4, and illto 35 of United States Patent 2,223,948. The pH of these products runsfrom about 2.0 to 10.4. Still other useful boric acid esters are thoseof 1,2,3,4,5-pentahydroxyhexane. persitol, volemitol,octahydroxyoctanes, nonahydroxynonanes, conyiene glycol, xylyleneglycol. inositol, cyclohexane-diol, etc. Mixtures or two or more of suchesters and/or salts or boric acid can be used.

The invention is not limited to cellulose derivative film supports butmaybe used with any type 0! support. It is especially useful withhydrotact thntit provides photographic elements with strongly adherentsynthetic hydroxyl polymer layers. It provides a rapid and commerciallypractical method of gelling such layers.

Another advantage of the invention is that it provides a simple methodfor gelling polymeric hydroxyallrane silver halide emulsion layers. Afurther advantage is that the gelling of such layers can be eihclentlycontrolled. A still further advantage is that it simplifies coatingoperations in that the emulsions do not substantially vary in viscosityduring coating operations. Since the gelling agents are not added to thecoating solutions oi the silver halide emulsions, there is no danger ofhaving them set up or gel prior to coating. A iurther advantage residesin the fact that no color is imparted from the novel gelling agents. Thegelling takes eiiect from the bottom of the coated layer upwardly givinga uniform product.

amass The action is very rapid and gelling takes-place as the coatingsolution is applied tothe layer contalning'the gelling agent.

As many apparently widely dii'ierentembodi merits of this invention maybe made without departing from the spirit and scope thereof; it is to beunderstood that the invention is not to 5011211! ited except as definedby the appended claims.

groups and said vinylpyridinepolymer beihg' soluble in 1% aqueous aceticacid.

2. A photographic element comprising a transparent support, a sublayeron said support composed oi water lnsoluble film-forming 'vinylpyridinepolymer which is soluble in "1% aqueous acetic acid, an intermediatelayer composed of a synthetic hydroxyl polymer containing a solubleboron compound capable oi yielding borate ions on said sublayer and agelled synthetic hydrcxyl polymer-silver halide'emulsion layer on theintermediate layer, said hydroxyl polymer contain ing a plurality ofrecurring intralinear CHaGHOH-- groups.

3. A photographic element comprising a transparent, flexible,hydrophobic fllm support, a sublayer on said support composed ofwater-insoluble film-forming vinylpyridine polymer which is soluble in1% aqueous acetic acid, an intermediate layer composed of a synthetichydroxyl polymer containing a soluble boron compound capable'oi yielding'borate ions on said sublaycr and a gelled synthetic hydroxyl polymersilver halide emulsion layer on the intermediate layer, said hydroxylpolymer containing a plurality of recurring intralinear CH2CHOH groups.

4. A photographic element comprising a sup-: port, a water-insolublefilm-forming vinylpyridine polymer sublayer on said support, ahydrogihilic hydrolyzed ethylene/vinyl acetate in terpolymerintermediate layer on said "support.

containing a soluble boron compound capable of yielding -borate ions onsaid sublayer and a gelled hydrophilic hydrolyzed ethylene/vinyl acetateinterpolymer silver halide emulsion layer on said intermediate layersaid vinylpyridine polymer he soluble in 1% aqueous acetic acid.

5. A photographic element comprising a paper support, a water-insolublefilm iorming vinylpyr-v ldlne polymer sublayer on said support, ahydrophilic hydrolyzed ethylene/vinyl acetate interpolymerintermedioterlayer onisaid support containing a .soluble- 'boroncompound capable of yielding boi'ate ions on said sublayer and a gelledhydrophilic hydrolyzed ethylene/vinyl acetate interpolymer silver halideemulsion layer on said intermediate layer said-vinylpyridine polymerbeing soluble in 1% aqueous acetic acid.

6. Aiph'otographic element comprising a support,- a sublayer on saidsupport composed of watier-insoluble-=polyvinylpyridine which is solublein 11% aqueous acetic acid, an intermediate layer comiposedzoi asynthetic-hydroxyl polymer containing a 1 soluble boron compound capableof yielding borate ionaon said sublayer and a gelled synthetic hydroxylpolymer silver halide emulsion layeri on the intermediate layer, saidhydrozqrl-polymer containing a plurality of recurring intralinear--CHr-CHOH- groups.

7. An element as set .forth in claim 6 wherein the boron compound is "aboric acid ester.- 01 a polyhydric alcohol.

8. The process of manufacturing photographic elements which comprisescoating a'suppbrt with a sublayer oomposed oi'va water-insolublefilmforming' vinylpyridine polymer which is soluble in 1% aqueous-aceticacid, coating said sublayer with an edueous' solution containing asynthetic hydroxyl polymer and a soluble boron compound capable ofyielding borate ions, coating the intermediate-layer formed with asynthetic hydroxyl polymer silver halideemulsion and adjusting the pH otthe coated layersto more than 7.5 said hydrpityl polymer containing aplurality of recurring intralinear T HiH Ofi oupsv 9.- The process ofmanufacturing protographic elements which-comprises-coating a support.with a sublayer composed of awater-insoluble fllmiorming vinyi ridinepolymer which is. soluble in 1% aqueous 'acetic --acid, coating saidsublayer with an aqueous solution containing a synthetic hydroxylpolymer and-.asolu'ble boron compound capable of yielding borate ions,and having a pH or notmore than 6 and coating the intermediate layerwith an alkaline's'ynthetic hydroxyl polymer silver halide emulsionhaving a pH greater than 7.5 said hyglrpxylpolymercontaining a pluralityof, recurring intralinear -CHrJlHOH groups.

CHARLES F. GLICK.

REFERENCES crrnn The following references are of recordfin the file ofthis patent:

. UNITED STATES PATENTS Number Name Date- 2,119,'l24 Staud June 7, 19382,397,885 Jennings Apr. 2, 1946

